The present invention relates generally to disposable wet wiping cloths and the like. More particularly, it is concerned with a new and improved nonwoven fibrous web material having sufficient wet strength to be used as a wet wipe, yet is capable of disintegration within a septic system after a brief period of time.
Wiping material of this type typically is prepackaged in a moist environment and is commonly used by consumers for cleansing or wiping parts of the body, particularly when wash water is not readily available or cannot be conveniently used. Travelers find such wipes especially convenient. These wipes have been used for applying or removing makeup or in cleansing other parts of the body, for example, as a substitute for conventional dry toilet paper.
As will be appreciated, these premoistened wipes often are disposed of through a sewer or septic system. Thus, while they must have sufficient wet strength to resist tearing and puncturing during use, they also must easily and readily disintegrate within the disposal systems and preferably, when disintegrated, be totally biodegradable. Disposable wipes of this type for personal hygienic use have been known for some time. Typically, they consist of nonwoven webs of fibrous material saturated with a cleansing solution and packaging in their wet condition for easy dispensing. The sheet material is stacked and wrapped in a liquid type package together with a wetting liquid that often includes bacteriacides and other biological control agents as well as perfumes, organism growth inhibitors, and the like.
Some wet wipes described heretofore have utilized a pH sensitive water soluble binder adhesive to achieve the requisite wet strength during packaging and use. The binders of such systems exhibit a resistance to weakening during storage, but are much more loosely bonded when the wipe has been immersed in a relatively large amount of substantially neutral water, allowing the wipe to readily break up in the turbulent water movement of the septic or sewer system. One such wet wipe is described in Adams et al U.S. Pat. No. 4,117,187 issued Sep. 26, 1978. Others have suggested the complete elimination of any binder system and rely instead on the hydroentanglement of the fibers within the wet wipe to achieve the requisite strength to process the web into a premoistened towelette for one time use. Such wet wipes readily disentangle when exposed to mild agitation so that they can be readily disposed of in the sewer and septic systems. A wipe of this type is described in U.S. Pat. No. 4,755,421, the disclosure of which is incorporated herein by reference. That patent describes a binder free hydroentangled web material consisting essentially of a blend of rayon fibers and papermaking pulp. While such materials exhibit acceptable absorption characteristics, the strength of such materials, particularly the wet strength thereof, is relatively poor as will be appreciated from the very rapid disintegration or breakup times exhibited by such materials.
Unfortunately, the addition of wet strength agents to nonwoven fibrous web materials to improve the wet properties of those materials significantly and deleteriously reduces the absorption characteristics of the fibrous web materials.